The invention relates to the technical field of landscaping and provides a garden plant planting method aiming at the problem of difficulty in nutrient absorption of tree seedlings. The garden plant planting method includes steps: S1 tree seedling pretreatment; S2, planting soil preparation; S3, planting pretreatment; S4, tree seedling planting. A soil additive is prepared from, by mass, 15-20 parts of urea, 1-2 parts of metalaxyl, 0.3-0.5 part of vermiculite, 0.5-1 part of eucalyptus leaf extract, 10-15 parts of metal salt, 50-55 parts of fertilizers, 1.5-2 parts of aminobenzoic acid, 0.1-0.5part of phenylbutyric acid and 0.5-1 part of potassium ortho-nitrophenolate. By adoption of rooting solution for pretreatment of tree seedling roots and adoption of planting soil for wrapping the tree seedling roots prior to tree seedling planting, rooting of the tree seedlings can be better promoted while the tree seedling growth speed is increased, subsequent maintenance of garden plants is avoided while the tree seedling survival rate is increased, simplicity and convenience in operation are achieved, and reduction of subsequent maintenance cost is benefited.